Inter-cell, as well as intra-cell, co-channel interference mitigation is one of the most critical tasks of the long term evolution (LTE) user equipment (UE) receiver in order to optimize downlink (DL) throughput and to minimize radio link failures. When optimizing UE receiver performance or when trading off performance against UE receiver power consumption and/or UE cost, mitigation of co-channel interference will benefit from network assistance: this means that the LTE network provides side information or coordination or both in combination in order to simplify, enable, or optimize interference cancelation (IC) or interference suppression (IS) in the UE receiver. The network assistance information is referred to as “IC/IS side information”, and an assumption may be made that the (1) Modulation order and (2) Precoder information (like codebook, #TX, #Mayers, PMI) of an interfering signal is useful IC/IS side information to provide to the UE receiver. For instance: with such IC/IS side info, a maximum likelihood detector in the UE which detects resource blocks and may be capable of also demodulating the interfering signal which is falling in the allocated resource blocks of the desired UE enabling an ideally complete elimination of the UE allocation's signal improving DL throughput of the interfering UE. Research results for specific intra-cell co-channel interference from MU-MIMO use case as well as for specific instances of the Heterogeneous Network (Hetnet) use case exist. Thus, network assistance to date has been exploited in specific use cases and with rather low granularity needs. Also, the study of the principle of providing network assistance and IC/IS side information has recently been initiated.
With respect to the inter-cell and intra-cell co-channel interference case in deployment scenarios and in particular in the homogeneous macro network certain problems have neither been considered nor solved to date. For example, appropriate/efficient method(s) for signaling IC/IS side information to the LTE UE for the general inter-cell co-channel interference case have not been developed. In particular, methods meeting the signaling requirements, minimizing changes to the LTE standard and/or UE receiver implementation, and optimizing network assistance have not been addressed. Further, methods for addressing the minimization of the amount of IC/IS side information has not been developed. In particular, minimizing the amount of resources required for providing network assistance information has not been addressed, wherein gains from IC/IS side information may be undermined.
The type of interference a UE experiences may vary from PRB to PRB as well as from TTI to TTI. Furthermore, the type of interference experienced by a UE depends on the type of allocations that UEs in the neighbor cells received from their serving eNB. RAS side information must exhibit a time-frequency granularity of one PRB and one TTI currently considered infeasible using existing methods.
Network assistance to date has been exploited in specific use cases and with rather low granularity needs. Also, the principle of providing network assistance and IC/IS side info has been proposed as 3GPP Study Item currently being under consideration for LTE Rel-12 but related work has not started yet. In particular no proposals are known that address how to integrate such IC/IS side info into the LTE system in a way that requires little additional implementation and nicely fits into the standard.
Alternative solution to assisting the UE receiver consists in pre-coding and coordination by the network. For example, coordinated multipoint (COMP) transmission and reception techniques utilize multiple transmit and receive antennas from multiple antenna site locations, which may or may not belong to the same physical cell, to enhance the received signal quality as well as decrease the received spatial interference. Multiple points coordinate with each other in such a way that the transmission signals from/to other points do not incur serious interference or even may be exploited as a meaningful signal. However, CoMP has thus far provided rather disappointing outcome from overall system performance point of view.